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This invention relates to load handling systems, specifically to block and tackle pulley arrangements.
Block and tackle pulley arrangements are commonly used to provide a mechanical advantage in raising, lowering, and moving loads. Typically, these arrangements involve the passing of a cord, rope, or cable through two sets of pulleys set in housings (blocks,) one of which (the fixed block) is attached to an immobile point such as a crane, tripod, or other fixed component. The second (or moving) block is typically directly attached to the load involved. By pulling on the rope, a mechanical advantage (determined by the number of pulleys utilized) is applied to move the load.
In the typical current embodiment, the limitation of this system is that by fixing the moving block to the load itself, the length of rope required to move the load is determined by multiplying the distance from the load to the fixed block by the ratio of mechanical advantage to be applied. That is, if a load is 100 feet from the fixed block, and a mechanical advantage of 3:1 is applied by threading a rope three times through three different pulleys, then 300 feet of rope is required to make the system operate.
Although in certain industrial applications, this limitation is commonly overcome through the use of longer ropes or cables, there are many applications where this limitation is difficult to overcome. Such applications include, but are not limited to, rock climbing, mountaineering, high angle or confined space rescue, small-craft marine applications, and logging or other backcountry load handling situations. These applications are typically limited with regard to weight or logistics to the lengths of rope that can be applied to handling loads.
Another ramification of pulley systems requiring long lengths of rope to operate is replacement costs for rope. Ropes in pulley systems currently in use for rescue applications are typically replaced on a regular basis regardless of wear or amount of use. Pulley systems that require a large amount of rope incur an increased cost, related to the replacement of the rope, over the lifetime of the system.
Another embodiment that is in current use is the xe2x80x98inch-wormxe2x80x99 or the piggy-backed z-pulley system. Both of these systems use multiple pulleys and a set of rope-grabs (or climbing ascenders) to generate mechanical advantage while minimizing the amount of rope that is required. The major disadvantage of this type of hauling system is the need for multiple anchor points for each of these pieces of equipment and a greatly increased complexity of rigging. These types of systems are typically very time consuming and complex to set up.
Various other disclosures of rope or clamps in combination with pulleys are shown in the following references:
None of the foregoing references are structurally similar the device of the present invention or accomplish the end goals in the same manner nor as efficiently, as each of these refer to pulley systems in which the moving block housing is directly attached to the load.
Accordingly, several objects and advantages of the present invention are:
a. to provide a block and tackle pulley system that applies equivalent mechanical advantage in moving a load as the prior art;
b. to provide a weight and space-efficient block and tackle pulley system that can be used in man-packed, confined-space situations, or weight-critical situations;
c. to provide a block and tackle pulley system that can be used with a minimal length of rope;
d. to provide a block and tackle pulley system that can be rigged from a single anchor point, and
e. to provide a block and tackle pulley system that can be set-up very simply and quickly.
Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
In accordance with the present invention a pulley system comprises a stationary-block housing and a moving-block housing each having at least one pulley and a gripping means.